MILWAUKEE--Even Harley-Davidson has its secrets. Inside the recesses of the company's archives and housed near the Harley-Davidson Museum complex here, a sort of motorcycle "X-Files" hides away. The collection includes a varied array of strange and iconic items connected to both the company and overall biker culture.

Some of those odd items have been assembled into Collection X, an exhibit on display through August 22. During a recent trip to both the Powertrain Operations factory and the Harley-Davidson Museum, CNET got to spy on Collection X, which offers insights into extreme machines that scored incredible achievements and bizarre creations forged out of a love for motorcycles.

Displays include the 1985 FXRP "Transamazon" motorcycle that Charles Peet raced 9,000 miles in 26 days across the width of South America, and the 1970 Land Speed Streamliner that Cal Rayborn piloted to the then land-speed record of more than 265 mph at the Bonneville Salt Flats in Utah.

But the most bizarre item in the collection might be the 2000 Red Moon Evo Chopper. At first glance, the high-handlebar bike looks like it's made of wood, a life-size tinker toy. But, it's actually covered in fine, warm-hued leather. It took 20 Japanese artists two years to hand-stitch the hide over every inch of the motorcycle, including engine components like the spark plugs and fuel valve.

You can get your own look at Collection X in our gallery above.

The Collection X exhibit at the Harley-Davidson Museum explored the bizarre side of motorcycle culture.
John Scott Lewinski/CNET